Variable magnification optical system, optical apparatus, imaging apparatus and method for manufacturing variable magnification optical system

ABSTRACT

A variable magnification optical system includes a positive first lens group disposed at a most object side, a negative intermediate group disposed at an image side of the first lens group, a positive focusing group disposed at an image side of the intermediate group, and a positive image side group disposed at an image side of the focusing group. Upon varying magnification, a distance between the first lens group and the intermediate group, a distance between the intermediate group and the focusing group and a distance between the focusing group and the image side group are varied; and the image side group includes, in order from an object side, a positive A group, a negative B group satisfying a predetermined conditional expression with respect to the A group, and a C group, whereby excellent optical performance, high speed focusing, and other advantages are achieved.

TECHNICAL FIELD

The present invention relates to a variable magnification opticalsystem, an optical apparatus, an imaging apparatus and a method formanufacturing the variable magnification optical system.

BACKGROUND ART

There has been proposed a variable magnification optical system that issuitable to be used for a photographic camera, an electronic stillcamera, a video camera and the like. For example, please refer to aJapanese Patent application Laid-Open Gazette No. H4-293007. However, avariable magnification optical system as disclosed in the JapanesePatent application Laid-Open Gazette No. H4-293007 is not intended toreduce a focusing group in weight sufficiently and is not suitable forattain high speed focusing operation.

PRIOR ART REFERENCE Patent Document

Patent Document 1: Japanese Patent application Laid-Open Gazette No.H4-293007.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda variable magnification optical system comprising a first lens groupdisposed at a most object side and having positive refractive power,

an intermediate group disposed at an image side of the first lens groupand having negative refractive power,

a focusing group disposed at an image side of the intermediate group andhaving positive refractive power, the focusing group being moved uponfocusing, and

an image side group disposed at an image side of the focusing group andhaving positive refractive power;

upon varying magnification, a distance between the first lens group andthe intermediate group, a distance between the intermediate group andthe focusing group and a distance between the focusing group and theimage side group being varied; and

the image side group comprising, in order from an object side, an Agroup having positive refractive power, a B group satisfying thefollowing conditional expression with respect to the A group and havingnegative refractive power, and a C group:

1.67<fA/(−fB)<2.80

where fA denotes a focal length of the A group,

and fB denotes a focal length of the B group.

Further, according to a second aspect of the present invention, there isprovided a method for manufacturing a variable magnification opticalsystem comprising steps of

arranging a first lens group disposed at a most object side and havingpositive refractive power, an intermediate group disposed at an imageside of the first lens group and having negative refractive power, afocusing group disposed at an image side of the intermediate group andhaving positive refractive power, the focusing group being moved uponfocusing, and an image side group disposed at an image side of thefocusing group and having positive refractive power such that, uponvarying magnification, a distance between the first lens group and theintermediate group, a distance between the intermediate group and thefocusing group and a distance between the focusing group and the imageside group are varied; and

arranging such that the image side group is composed of, in order froman object side, an A group having positive refractive power, a B groupsatisfying the following conditional expression with respect to the Agroup and having negative refractive power, and a C group:

1.67<fA/(−fB)<2.80

where fA denotes a focal length of the A group,

and fB denotes a focal length of the B group.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a variable magnification optical systemaccording to a First Example.

FIGS. 2A, 2B and 2C are graphs showing various aberrations of thevariable magnification optical system according to the First Example.

FIGS. 3A and 3B are graphs showing meridional transverse aberrations ofthe variable magnification optical system according to the FirstExample.

FIGS. 4A, 4B and 4C are graphs showing various aberrations of thevariable magnification optical system according to the First Example.

FIG. 5 is a sectional view of a variable magnification optical systemaccording to a Second Example.

FIGS. 6A, 6B and 6C are graphs showing various aberrations of thevariable magnification optical system according to the Second Example.

FIGS. 7A and 7B are graphs showing meridional transverse aberrations ofthe variable magnification optical system according to the SecondExample.

FIGS. 8A, 8B and 8C are graphs showing various aberrations of thevariable magnification optical system according to the Second Example.

FIG. 9 is a sectional view of a variable magnification optical systemaccording to a Third Example.

FIGS. 10A, 10B and 10C are graphs showing various aberrations of thevariable magnification optical system according to the Third Example.

FIGS. 11A and 11B are graphs showing meridional transverse aberrationsof the variable magnification optical system according to the ThirdExample.

FIGS. 12A, 12B and 12C are graphs showing various aberrations of thevariable magnification optical system according to the Third Example.

FIG. 13 is a sectional view of a variable magnification optical systemaccording to a Fourth Example.

FIGS. 14A, 14B and 14C are graphs showing various aberrations of thevariable magnification optical system according to the Fourth Example.

FIGS. 15A and 15B are graphs showing meridional transverse aberrationsof the variable magnification optical system according to the FourthExample.

FIGS. 16A, 16B and 16C are graphs showing various aberrations of thevariable magnification optical system according to the Fourth Example.

FIG. 17 is a sectional view of a variable magnification optical systemaccording to a Fifth Example.

FIGS. 18A, 18B and 18C are graphs showing various aberrations of thevariable magnification optical system according to the Fifth Example.

FIGS. 19A and 19B are graphs showing meridional transverse aberrationsof the variable magnification optical system according to the FifthExample.

FIGS. 20A, 20B and 20C are graphs showing various aberrations of thevariable magnification optical system according to the Fifth Example.

FIG. 21 is a sectional view of a variable magnification optical systemaccording to a Sixth Example.

FIGS. 22A, 22B and 22C are graphs showing various aberrations of thevariable magnification optical system according to the Sixth Example.

FIGS. 23A and 23B are graphs showing meridional transverse aberrationsof the variable magnification optical system according to the SixthExample.

FIGS. 24A, 24B and 24C are graphs showing various aberrations of thevariable magnification optical system according to the Sixth Example.

FIG. 25 is a sectional view of a variable magnification optical systemaccording to a Seventh Example.

FIGS. 26A, 26B and 26C are graphs showing various aberrations of thevariable magnification optical system according to the Seventh Example.

FIGS. 27A and 27B are graphs showing meridional transverse aberrationsof the variable magnification optical system according to the SeventhExample.

FIGS. 28A, 28B and 28C are graphs showing various aberrations of thevariable magnification optical system according to the Seventh Example.

FIG. 29 is a sectional view of a variable magnification optical systemaccording to an Eighth Example.

FIGS. 30A, 30B and 30C are graphs showing various aberrations of thevariable magnification optical system according to the Eighth Example.

FIGS. 31A and 31B are graphs showing meridional transverse aberrationsof the variable magnification optical system according to the EighthExample.

FIGS. 32A, 32B and 32C are graphs showing various aberrations of thevariable magnification optical system according to the Eighth Example.

FIG. 33 shows a configuration of a camera equipped with the variablemagnification optical system.

FIG. 34 is a flowchart schematically explaining a method formanufacturing the variable magnification optical system.

EMBODIMENT FOR CARRYING OUT THE INVENTION

Next, a variable magnification optical system according to theembodiment of the present invention, an optical apparatus, an imagingapparatus and a method for manufacturing the variable magnificationoptical system, will be explained.

The variable magnification optical system according to the presentembodiment comprises a first lens group disposed at a most object sideand having positive refractive power, an intermediate group disposed atan image side of the first lens group and having negative refractivepower, a focusing group disposed at an image side of the intermediategroup and having positive refractive power, the focusing group beingmoved upon focusing, and an image side group disposed at an image sideof the focusing group and having positive refractive power; upon varyingmagnification, a distance between the first lens group and theintermediate group, a distance between the intermediate group and thefocusing group and a distance between the focusing group and the imageside group being varied; and the image side group being composed of, inorder from an object side, an A group having positive refractive power,a B group satisfying the following conditional expression (1) withrespect to the A group and having negative refractive power, and a Cgroup:

1.67<fA/(−fB)<2.80   (1)

where fA denotes a focal length of the A group, and

fB denotes a focal length of the B group.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the focusing group is composedof one or two lens components.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the B group is disposed to bemovable to have a displacement component in a direction perpendicular tothe optical axis.

The focusing group of the present embodiment comprises at least one lensgroup. Further, the image side group of the present embodiment comprisesat least one lens group. Furthermore, each of the A group, the B groupand the C group of the present embodiment comprises at least one lens.Meanwhile, the term “lens group” in the present embodiment is a portioncomprising at least one lens separated by an air space which varies uponvarying magnification. Further, distance(s) between lenses included inlens groups in the present embodiment, is(are) not varied upon varyingmagnification, but is(are) changeable properly.

As described above, the variable magnification optical system accordingto the present embodiment comprises at least four lens groups and variesdistances between lens groups upon varying magnification. With thisconfiguration, it is possible to correct superbly various aberrationsupon varying magnification.

Further, in the variable magnification optical system according to thepresent embodiment, as described above, the focusing group is composedof one or two lens components. With such configuration, the focusinggroup can be downsized and reduced in weight. Meanwhile, the term “lenscomponent” in the present embodiment means a single lens or a cementedlens. Further, in the variable magnification optical system according tothe present embodiment, the focusing group means a portion comprising atleast one lens separated by an air space that changes upon focusing.

Furthermore, in the variable magnification optical system according tothe present embodiment, as described above, the image side group iscomposed of, in order from the object side, the A group having positiverefractive power, the B group having negative refractive power, and theC group, the B group being moved, as a vibration reduction group, tohave a displacement component in a direction perpendicular to theoptical axis. With such configuration, it is possible to correctdisplacement of imaging position caused by a camera shake or the like,in other words, vibration reduction can be carried out. Moreover, thevibration reduction group can be downsized, and in addition theretodeterioration in optical performance upon carrying out vibrationreduction can be effectively suppressed. Meanwhile, the vibrationreduction group in the present embodiment means a portion that is movedto have a component in a direction perpendicular to the optical axisupon carrying out vibration reduction.

The above conditional expression (1) defines a ratio of the focal lengthof the A group to the focal length of the B group that is the vibrationreduction group. With satisfying the conditional expression (1), thevariable magnification optical system according to the presentembodiment can suppress effectively deterioration in optical performanceupon carrying out vibration reduction.

When the value of fA/(−fB) is equal to or exceeds the upper limit valueof the conditional expression (1) of the variable magnification opticalsystem according to the present embodiment, refractive power of thevibration reduction group becomes large, and deterioration in eccentriccoma aberration upon carrying out vibration reduction becomes large.Meanwhile, in order to ensure the advantageous effect of the presentembodiment, it is preferable to set the upper limit value of theconditional expression (1) to 2.70. Further, in order to ensure theadvantageous effect of the present embodiment more surely, it ispreferable to set the upper limit value of the conditional expression(1) to 2.60.

On the other hand, when the value of fA/(−fB) is equal to or falls belowthe lower limit value of the conditional expression (1) of the variablemagnification optical system according to the present embodiment,refractive power of the A group becomes large, and it becomes difficultto correct spherical aberration and other various aberrations. Further,refractive power of the vibration reduction group becomes small, and anamount of movement of the vibration reduction group upon carrying outvibration reduction becomes large. For this reason, a lens barrel thatreceives the variable magnification optical system according to thepresent embodiment becomes large in size, so this is not preferable.Meanwhile, in order to ensure the advantageous effect of the presentembodiment, it is preferable to set the lower limit value of theconditional expression (1) to 1.68. Furthermore, in order to ensure theadvantageous effect of the present embodiment more surely, it ispreferable to set the lower limit value of the conditional expression(1) to 1.69.

With configurations as described above, it is possible to realize avariable magnification optical system having excellent opticalperformance and a focusing lens group reduced in weight in order toattain high speed focusing operation.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that a distance between the A groupand the B group is larger than a distance between the B group and the Cgroup.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the following conditionalexpression (1A) is satisfied:

2.50<f1/(−fc)<6.20   (1A)

where f1 denotes a focal length of the first lens group, and fc denotesa focal length of the intermediate group.

The conditional expression (1A) defines a ratio of the focal length ofthe first lens group to the focal length of the intermediate group. Withsatisfying the conditional expression (1A), the variable magnificationoptical system according to the present embodiment can suppressvariations in spherical aberration and other various aberrations uponvarying magnification from a wide angle end state to a telephoto endstate.

When the value of f1/(−fc) is equal to or exceeds the upper limit valueof the conditional expression (1A) of the variable magnification opticalsystem according to the present embodiment, refractive power of theintermediate group becomes large, and it becomes difficult to correctspherical aberration and other various aberrations. Meanwhile, in orderto ensure the advantageous effect of the present embodiment, it ispreferable to set the upper limit value of the conditional expression(1A) to 5.90. Further, in order to ensure the advantageous effect of thepresent embodiment more surely, it is preferable to set the upper limitvalue of the conditional expression (1A) to 5.60.

On the other hand, when the value of f1/(−fc) is equal to or falls belowthe lower limit value of the conditional expression (1A) of the variablemagnification optical system according to the present embodiment,refractive power of the first lens group becomes large, and it becomesdifficult to correct spherical aberration and other various aberrations.Meanwhile, in order to ensure the advantageous effect of the presentembodiment, it is preferable to set the lower limit value of theconditional expression (1A) to 2.80. Furthermore, in order to ensure theadvantageous effect of the present embodiment more surely, it ispreferable to set the lower limit value of the conditional expression(1A) to 3.70.

Further, in the variable magnification optical system according to thepresent embodiment it is desirable that the following conditionalexpression (1B) is satisfied:

3.00<f1fw/ff<9.00   (1B)

where f1fw denotes a composite focal length from the first lens group tothe focusing group in the wide angle end state, and ff denotes a focallength of the focusing group.

The conditional expression (1B) defines a ratio of the composite focallength from the first lens group to the focusing group in the wide angleend state to the focal length of the focusing group. With satisfying theconditional expression (1B), the variable magnification optical systemaccording to the present embodiment can suppress variations in sphericalaberration and other various aberrations upon focusing from aninfinitely distant object to a close distance object in the wide angleend state.

When the value of f1fw/ff is equal to or exceeds the upper limit valueof the conditional expression (1B) of the variable magnification opticalsystem according to the present embodiment, refractive power of thefocusing group becomes large, and it becomes difficult to suppressvariations in spherical aberration and other various aberrations uponfocusing from an infinitely distant object to a close distance object inthe wide angle end state. Meanwhile, in order to ensure the advantageouseffect of the present embodiment, it is preferable to set the upperlimit value of the conditional expression (1B) to 8.50. Further, inorder to ensure the advantageous effect of the present embodiment moresurely, it is preferable to set the upper limit value of the conditionalexpression (1B) to 8.00.

On the other hand, when the value of f1fw/ff is equal to or falls belowthe lower limit value of the conditional expression (1B) of the variablemagnification optical system according to the present embodiment,refractive power from the first lens group to the focusing group in thewide angle end state becomes large, and it becomes difficult to suppressvariations in spherical aberration and other various aberrations uponfocusing from an infinitely distant object to a close distance object inthe wide angle end state. Meanwhile, in order to ensure the advantageouseffect of the present embodiment, it is preferable to set the lowerlimit value of the conditional expression (1B) to 3.30. Furthermore, inorder to ensure the advantageous effect of the present embodiment moresurely, it is preferable to set the lower limit value of the conditionalexpression (1B) to 3.60.

Further, in the variable magnification optical system according to thepresent embodiment it is desirable that the following conditionalexpression (2) is satisfied:

1.50<f1/ff<2.35   (2)

where f1 denotes a focal length of the first lens group, and ff denotesa focal length of the focusing group.

The conditional expression (2) defines a ratio of the focal length ofthe first lens group to the focal length of the focusing group. Withsatisfying the conditional expression (2), the variable magnificationoptical system according to the present embodiment can suppressvariations in spherical aberration and other various aberrations uponcarrying out focusing from an infinitely distant object to a closedistance object.

When the value of f1/ff is equal to or exceeds the upper limit value ofthe conditional expression (2) of the variable magnification opticalsystem according to the present embodiment, refractive power of thefocusing group becomes large, and it becomes difficult to suppressvariations in spherical aberration and other various aberrations uponcarrying out focusing from an infinitely distant object to a closedistance object. Meanwhile, in order to ensure the advantageous effectof the present embodiment, it is preferable to set the upper limit valueof the conditional expression (2) to 2.30. Further, in order to ensurethe advantageous effect of the present embodiment more surely, it ispreferable to set the upper limit value of the conditional expression(2) to 2.25.

On the other hand, when the value of f1/ff is equal to or falls belowthe lower limit value of the conditional expression (2) of the variablemagnification optical system according to the present embodiment,refractive power of the first lens group becomes large, and it becomesdifficult to correct spherical aberration and other various aberrations.Meanwhile, in order to ensure the advantageous effect of the presentembodiment, it is preferable to set the lower limit value of theconditional expression (2) to 1.60. Furthermore, in order to ensure theadvantageous effect of the present embodiment more surely, it ispreferable to set the lower limit value of the conditional expression(2) to 1.70.

Further, in the variable magnification optical system according to thepresent embodiment it is desirable that the first lens group is movedtoward the object side upon varying magnification from the wide angleend state to the telephoto end state. With such a configuration, thewhole length of the variable magnification optical system according tothe present embodiment can be reduced in the wide angle end state,thereby it becoming possible to downsize the variable magnificationoptical system according to the present embodiment.

Further, in the variable magnification optical system according to thepresent embodiment it is desirable that a distance between the focusinggroup and the image side group is increased upon varying magnificationfrom the wide angle end state to the telephoto end state. With thisconfiguration, various aberrations upon varying magnification can becorrected superbly. In particular, it is possible to secure sufficientlya space for moving the focusing group for focusing in the telephoto endstate, so it is possible to correct excellently spherical aberrationupon focusing on a close distance object in the telephoto end state.

Further, in the variable magnification optical system according to thepresent embodiment it is desirable that the following conditionalexpression (3) is satisfied:

0.25<ff/fi<1.10   (3)

where ff denotes a focal length of the focusing group, and fi denotes afocal length of the image side group.

The conditional expression (3) defines a ratio of the focal length ofthe focusing group to the focal length of the image side group. Withsatisfying the conditional expression(3), the variable magnificationoptical system according to the present embodiment can suppressvariations in spherical aberration and other various aberrations uponfocusing from an infinitely distant object to a close distance object.

When the value of ff/fi is equal to or exceeds the upper limit value ofthe conditional expression (3) of the variable magnification opticalsystem according to the present embodiment, refractive power of theimage side group becomes large, and it becomes difficult to suppresscoma aberration and other various aberrations. Meanwhile, in order toensure the advantageous effect of the present embodiment, it ispreferable to set the upper limit value of the conditional expression(3) to 1.05. Further, in order to ensure the advantageous effect of thepresent embodiment more surely, it is preferable to set the upper limitvalue of the conditional expression (3) to 1.00.

On the other hand, when the value of ff/fi is equal to or falls belowthe lower limit value of the conditional expression (3) of the variablemagnification optical system according to the present embodiment,refractive power of the focusing group becomes large, and it becomesdifficult to correct variations in spherical aberration and othervarious aberrations upon focusing from an infinitely distant object to aclose distance object. Meanwhile, in order to ensure the advantageouseffect of the present embodiment, it is preferable to set the lowerlimit value of the conditional expression (3) to 0.28. Furthermore, inorder to ensure the advantageous effect of the present embodiment moresurely, it is preferable to set the lower limit value of the conditionalexpression (3) to 0.31.

Further, in the variable magnification optical system according to thepresent embodiment it is desirable that the following conditionalexpression (4) is satisfied:

1.80<fi/(−fB)<5.20   (4)

where fi denotes a focal length of the image side group, and fB denotesa focal length of the B group.

The conditional expression (4) defines a ratio of the focal length ofthe image side group to the focal length of the B group that is thevibration reduction group. With satisfying the conditional expression(4), the variable magnification optical system according to the presentembodiment can suppress effectively deterioration of optical performanceupon carrying out vibration reduction.

When the value of fi/(−fB) is equal to or exceeds the upper limit valueof the conditional expression (4) of the variable magnification opticalsystem according to the present embodiment, refractive power of thevibration reduction group becomes large, and deterioration of eccentriccoma aberration upon carrying out vibration reduction becomes large.Meanwhile, in order to ensure the advantageous effect of the presentembodiment, it is preferable to set the upper limit value of theconditional expression (4) to 5.00. Further, in order to ensure theadvantageous effect of the present embodiment more surely, it ispreferable to set the upper limit value of the conditional expression(4) to 4.90.

On the other hand, when the value of fi/(−fB) is equal to or falls belowthe lower limit value of the conditional expression (4) of the variablemagnification optical system according to the present embodiment,refractive power of the image side group becomes large, and it becomesdifficult to correct coma aberration and other various aberrations.Further, refractive power of the vibration reduction group becomessmall, and an amount of movement of the vibration reduction group uponcarrying out vibration reduction becomes large. For this reason, a lensbarrel that receives the variable magnification optical system accordingto the present embodiment becomes large in size, so this is notpreferable. Meanwhile, in order to ensure the advantageous effect of thepresent embodiment, it is preferable to set the lower limit value of theconditional expression (4) to 1.90. Further, in order to ensure theadvantageous effect of the present embodiment more surely, it ispreferable to set the lower limit value of the conditional expression(4) to 2.00.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the first lens group comprisesat least two positive lenses. With this configuration, sphericalaberration and chromatic aberration can be corrected effectively.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the focusing group is composedof one lens component. With this configuration, the focusing group canbe made smaller in size and made lighter in weight.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the focusing group is composedof one single lens. With this configuration, the focusing group can bemade lighter in weight.

Further, in the variable magnification optical system according to thepresent embodiment, it is desirable that the focusing group comprises atleast one positive lens and the following conditional expression (5) issatisfied:

58.00<νFP   (5)

where νFP denotes an Abbe number for d-line (wavelength 587.6 nm) of thepositive lens comprised in the focusing group.

The conditional expression (5) defines an Abbe number of the positivelens comprised in the focusing group. With satisfying the conditionalexpression (5), the variable magnification optical system according tothe present embodiment can suppress variation in chromatic aberrationupon focusing from an infinitely distant object to a close distanceobject.

When the value of νFP is equal to or falls below the lower limit valueof the conditional expression (5) of the variable magnification opticalsystem according to the present embodiment, large chromatic aberrationin the focusing group occurs, so that variation in chromatic aberrationupon focusing from an infinitely distant object to a close distanceobject becomes large. Meanwhile, in order to ensure the advantageouseffect of the present embodiment, it is preferable to set the lowerlimit value of the conditional expression (5) to 59.00. Furthermore, inorder to ensure the advantageous effect of the present embodiment moresurely, it is preferable to set the lower limit value of the conditionalexpression (5) to 60.00.

Further, in the variable magnification optical system according to thepresent embodiment it is desirable that the following conditionalexpression (6) is satisfied:

0.15<ff/ft<0.30   (6)

where ff denotes a focal length of the focusing group, and ft denotes afocal length of the variable magnification optical system in thetelephoto end state.

The conditional expression (6) defines a ratio of the focal length ofthe focusing group to the focal length of the variable magnificationoptical system according to the present embodiment in the telephoto endstate. With satisfying the conditional expression (6), the variablemagnification optical system according to the present embodiment cansuppress variations in spherical aberration and other variousaberrations upon focusing from an infinitely distant object to a closedistance object.

When the value of ff/ft is equal to or exceeds the upper limit value ofthe conditional expression (6) of the variable magnification opticalsystem according to the present embodiment, an amount of movement of thefocusing group upon focusing from an infinitely distant object to aclose distance object becomes large, and it becomes difficult tosuppress variations in spherical aberration and other variousaberrations. Meanwhile, in order to ensure the advantageous effect ofthe present embodiment, it is preferable to set the upper limit value ofthe conditional expression (6) to 0.28. Further, in order to ensure theadvantageous effect of the present embodiment more surely, it ispreferable to set the upper limit value of the conditional expression(6) to 0.26.

On the other hand, when the value of ff/ft is equal to or falls belowthe lower limit value of the conditional expression (6) of the variablemagnification optical system according to the present embodiment,refractive power of the focusing group becomes large, and it becomesdifficult to correct variations in spherical aberration and othervarious aberrations upon focusing from an infinitely distant object to aclose distance object. Meanwhile, in order to ensure the advantageouseffect of the present embodiment, it is preferable to set the lowerlimit value of the conditional expression (6) to 0.17. Furthermore, inorder to ensure the advantageous effect of the present embodiment moresurely, it is preferable to set the lower limit value of the conditionalexpression (6) to 0.19.

An optical apparatus according to an embodiment of the present inventioncomprises a variable magnification optical system configured asabove-mentioned.

An imaging apparatus according to an embodiment of the present inventionis equipped with a variable magnification optical system configured asabove-mentioned and an imaging unit for capturing an image formed by thevariable magnification optical system.

With such configurations, it is possible to realize an optical apparatusand an imaging apparatus which have excellent optical performance and afocusing lens group reduced in weight in order to attain high speedfocusing operation.

According to an embodiment of the present invention, there is provided amethod for manufacturing a variable magnification optical systemcomprising steps of arranging a first lens group disposed at a mostobject side and having positive refractive power, an intermediate groupdisposed at an image side of the first lens group and having negativerefractive power, a focusing group disposed at an image side of theintermediate group and having positive refractive power, the focusinggroup being moved upon focusing, and an image side group disposed at animage side of the focusing group and having positive refractive powersuch that, upon varying magnification, a distance between the first lensgroup and the intermediate group, a distance between the intermediategroup and the focusing group and a distance between the focusing groupand the image side group are varied; and arranging such that the imageside group is composed of, in order from an object side, an A grouphaving positive refractive power, a B group satisfying the followingconditional expression (1) with respect to the A group and havingnegative refractive power, and a C group:

1.67<fA/(−fB)<2.80   (1)

where fA denotes a focal length of the A group, and

fB denotes a focal length of the B group.

With such configurations, it is possible to manufacture a variablemagnification optical system which has excellent optical performance anda focusing lens group reduced in weight in order to attain high speedfocusing operation.

Hereinafter, examples relating to a variable magnification opticalsystem according to an embodiment of the present invention will beexplained with reference to the accompanying drawings.

FIRST EXAMPLE

FIG. 1 is a sectional view of a variable magnification optical systemaccording to a First Example. Note that each arrow in FIG. 1 and FIGS.5, 9, 13, 17, 21, 25 and 29 as described later indicates movingtrajectory of each lens group upon varying magnification from the wideangle end state (W) to the telephoto end state (T).

The variable magnification optical system according to the First Exampleis composed of, in order from an object side, a first lens group G1having positive refractive power, a second lens group G2 having negativerefractive power, and a rear group GR having positive refractive power.The rear group GR is composed of, in order from the object side, a thirdlens group G3 having positive refractive power, and a fourth lens groupG4 having positive refractive power.

The first lens group G1 consists of, in order from the object side, adouble convex positive lens L11, and a cemented positive lensconstructed by a negative meniscus lens L12 having a convex surfacefacing the object side cemented with a positive meniscus lens L13 havinga convex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented negative lens constructed by a double concave negative lens L21cemented with a positive meniscus lens L22 having a convex surfacefacing the object side, and a double concave negative lens L23.

The third lens group G3 consists of a double convex positive lens L31.

The fourth lens group G4 is composed of, in order from the object side,an A group G4A having positive refractive power, a B group G4B havingnegative refractive power, and a C group G4C having positive refractivepower. Meanwhile, an aperture stop S is disposed between the A group G4Aand the B group G4B.

The A group G4A consists of, in order from the object side, a cementedpositive lens constructed by a double convex positive lens L41 cementedwith a double concave negative lens L42, and a double convex positivelens L43.

The B group G4B consists of, in order from the object side, a cementednegative lens constructed by a double convex positive lens L44 cementedwith a double concave negative lens L45.

The C group G4C consists of, in order from the object side, a doubleconvex positive lens L46, and a negative meniscus lens L47 having aconcave surface facing the object side.

In the variable magnification optical system according to the FirstExample, the first to fourth lens groups G1 to G4 are moved along theoptical axis so that, upon varying magnification between the wide angleend state and the telephoto end state, a distance between the first lensgroup G1 and the second lens group G2, a distance between the secondlens group G2 and the third lens group G3 and a distance between thethird lens group G3 and the fourth lens group G4 are varied.

In the variable magnification optical system according to the FirstExample, the third lens group

G3 is moved toward an image side along the optical axis, as the focusinglens group, thereby focusing from an infinitely distant object to aclose distance object.

In the variable magnification optical system according to the FirstExample, the B group G4B is moved, as a vibration reduction group, tohave a component in a direction perpendicular to the optical axis,thereby carrying out vibration reduction. Meanwhile, upon carrying outvibration reduction, positions of the A group G4A and the C group G4C ina direction perpendicular to the optical axis are fixed.

It is noted that in a lens having a focal length f of the whole lenssystem and a vibration reduction coefficient K (a ratio of a movingamount of an image on the image plane I to a moving amount of thevibration reduction group), it is possible to correct a rotationalcamera shake of an angle θ, by moving the vibration reduction group bythe amount of (f·tan θ)/K perpendicularly to the optical axis.Accordingly, in the variable magnification optical system according tothe First Example, in the wide angle end state, the vibration reductioncoefficient is 1.06, and the focal length is 71.40 (mm), so that themoving amount of the B group G4B for correcting a rotational camerashake of 0.30 degrees is 0.35 (mm). In the telephoto end state, thevibration reduction coefficient is 1.86, and the focal length is 294.00(mm), so that the moving amount of the B group G4B for correcting arotational camera shake of 0.20 degrees is 0.55 (mm).

Table 1 below shows various values of the variable magnification opticalsystem according to the First Example.

In table 1, “f” denotes a focal length, and “BF” denotes a back focallength (a distance on the optical axis between a most image side lenssurface and the image plane I).

In [Surface Data], a surface number denotes an order of an opticalsurface counted from the object side, “r” denotes a radius of curvature,“d” denotes a surface-to-surface distance (a distance from an n-thsurface to an (n+1)-th surface, where n is an integer), “nd” denotesrefractive index for d-line (wavelength 587.6 nm) and “νd” denotes anAbbe number for d-line (wavelength 587.6 nm). Further, “Object Plane”denotes an object surface, “variable” denotes a variablesurface-to-surface distance, “Stop S” denotes an aperture stop, and “I”denotes an image plane. Meanwhile, radius of curvature r=∞ denotes aplane surface. Refractive index of air nd=1.00000 is omitted.

In [Various Data], “FNO” denotes an F-number, “2ω” denotes an angle ofview (unit “°”), “Ymax” denotes a maximum image height, “TL” denotes atotal length of the variable magnification optical system according tothe First Example (a distance along the optical axis from the firstsurface to the image plane I), and “dn” denotes a variable distancebetween an n-th surface and an (n+1)-th surface. Meanwhile, “W” denotesa wide angle end state, “M” denotes an intermediate focal length state,“T” denotes a telephoto end state, “Infinitely distant” denotes a timewhen focusing on an infinitely distant object is conducted, and “Closedistance” denotes a time when focusing on a close distance object isconducted.

In [Lens Group Data], a starting surface and a focal length for eachlens group are shown.

In [Values for Conditional Expressions], values corresponding torespective conditional expressions of the variable magnification opticalsystem according to the First Example are shown.

Here, that “mm” is generally used for the unit of length such as thefocal length f, the radius of curvature r and the unit for other lengthsshown in Table 1. However, since similar optical performance can beobtained by an optical system proportionally enlarged or reduced in itsdimension, the unit is not necessarily to be limited to “mm”.

The reference symbols in Table 1 described above, are used in the sameway in Tables for the other Examples.

TABLE 1 First Example [Surface Data] Surface number r d nd νd ObjectPlane ∞  1 72.3688 6.972 1.51680 63.88  2 −604.5951 0.499  3 88.46751.500 1.62004 36.40  4 32.5526 8.844 1.51680 63.88  5 149.4554 variable 6 −453.8182 1.000 1.69680 55.52  7 18.7304 3.761 1.80518 25.45  840.0562 3.501  9 −33.7169 1.000 1.69680 55.52 10 3769.5898 variable 1191.7620 4.268 1.51680 63.88 12 −46.5887 variable 13 54.6217 5.3611.48749 70.31 14 −31.8367 1.000 1.85026 32.35 15 829.9126 0.200 1634.8197 4.124 1.48749 70.31 17 −190.4880 1.633 18 (Stop S) ∞ 27.478  19316.7035 2.575 1.80518 25.45 20 −37.0122 1.000 1.74400 44.81 21 28.10123.267 22 27.6380 3.921 1.54814 45.79 23 −54.2282 2.418 24 −22.4640 1.0001.77250 49.62 25 −55.2971 BF Image Plane ∞ [Various Data] Variablemagnification ratio 4.12 W M T f 71.4 105.0 294.0 FNO 4.17 4.18 6.38 2ω22.84 15.30 5.48 Ymax 14.25 14.25 14.25 TL 166.32 183.64 219.32 BF 38.5238.53 73.71 Infinitely distant d5 3.555 24.790 43.361 d10 26.610 21.6142.000 d12 12.316 13.381 14.933 Close distance d5 3.555 24.790 43.361 d1027.368 22.723 3.114 d12 11.558 12.271 13.819 [Lens Group Data] GroupStarting Surface f 1 1 115.478 2 6 −26.653 3 11 60.427 4 13 138.481[Values for Conditional Expression] (1) fA/(−fB) = 1.717 (1A) f1/(−fc) =4.333 (1B) f1fw/ff = 6.400 (2) f1/ff = 1.911 (3) ff/fi = 0.436 (4)fi/(−fB) = 3.064 (5) νFP = 63.88 (6) ff/ft = 0.206

FIGS. 2A, 2B and 2C are graphs showing various aberrations of thevariable magnification optical system according to the First Exampleupon focusing on an infinitely distant object, in which FIG. 2A is in awide angle end state, FIG. 2B is in an intermediate focal length state,and FIG. 2C is in the telephoto end state.

FIG. 3A is a graph showing meridional transverse aberration of thevariable magnification optical system according to the First Exampleupon focusing on an infinitely distant object in the wide angle endstate with carrying out vibration reduction against a rotational camerashake of 0.30 degrees, and FIG. 3B is a graph showing meridionaltransverse aberration of the variable magnification optical systemaccording to the First Example upon focusing on an infinitely distantobject in the telephoto end state with carrying out vibration reductionagainst a rotational camera shake of 0.20 degrees.

FIGS. 4A, 4B and 4C are graphs showing various aberrations of thevariable magnification optical system according to the First Exampleupon focusing on a close distance object, in which FIG. 4A is in thewide angle end state, FIG. 4B is in the intermediate focal length state,and FIG. 4C is in the telephoto end state.

In respective aberration graphs, FNO denotes an F-number, Y denotes animage height, and NA denotes a numerical aperture. For more information,there are shown a value of F-number FNO or numerical aperture NAcorresponding to the maximum diameter in a spherical aberration graph,the maximum value of the image height Y in each of an astigmatism graphand a distortion graph, and a value of each image height in a comaaberration graph. Additionally, in respective aberration graphs, ddenotes an aberration at d-line (wavelength 587.6 nm), and g denotes anaberration at g-line (wavelength 435.8 nm). In the astigmatism graph, asolid line indicates a sagittal image plane, and a broken line indicatesa meridional image plane. The coma aberration graph shows a comaaberration for each image height Y. Incidentally, the same symbols asused in the First Example are employed in the other Examples asdescribed later.

As is apparent from the respective aberration graphs, the variablemagnification optical system according to the First Example shows superbimaging performance as a result of good corrections to variousaberrations in the wide angle end state to the telephoto end state, andalso shows superb imaging performance upon carrying out vibrationreduction and upon focusing on a close distance object.

SECOND EXAMPLE

FIG. 5 is a sectional view of a variable magnification optical systemaccording to a Second Example.

The variable magnification optical system according to the SecondExample is composed of, in order from an object side, a first lens groupG1 having positive refractive power, a second lens group G2 havingnegative refractive power, and a rear group GR having positiverefractive power. The rear group GR is composed of, in order from theobject side, a third lens group G3 having positive refractive power, anda fourth lens group G4 having positive refractive power.

The first lens group G1 consists of, in order from the object side, adouble convex positive lens L11, and a cemented positive lensconstructed by a negative meniscus lens L12 having a convex surfacefacing the object side cemented with a positive meniscus lens L13 havinga convex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented negative lens constructed by a double concave negative lens L21cemented with a positive meniscus lens L22 having a convex surfacefacing the object side, and a double concave negative lens L23.

The third lens group G3 consists of a double convex positive lens L31.

The fourth lens group G4 is composed of, in order from the object side,an A group G4A having positive refractive power, a B group G4B havingnegative refractive power, and a C group G4C having positive refractivepower. Meanwhile, an aperture stop S is disposed between the A group G4Aand the B group G4B.

The A group G4A consists of, in order from the object side, a cementedpositive lens constructed by a double convex positive lens L41 cementedwith a negative meniscus lens L42 having a concave surface facing theobject side.

The B group G4B consists of, in order from the object side, a cementednegative lens constructed by a positive meniscus lens L43 having aconcave surface facing the object side cemented with a double concavenegative lens L44.

The C group G4C consists of, in order from the object side, a doubleconvex positive lens L45 and a negative meniscus lens L46 having aconcave surface facing the object side.

In the variable magnification optical system according to the SecondExample, the first to fourth lens groups G1 to G4 are moved along theoptical axis so that, upon varying magnification between the wide angleend state and the telephoto end state, a distance between the first lensgroup G1 and the second lens group G2, a distance between the secondlens group G2 and the third lens group G3 and a distance between thethird lens group G3 and the fourth lens group G4 are varied.

In the variable magnification optical system according to the SecondExample, the third lens group G3 is moved toward an image side along theoptical axis, as the focusing lens group, thereby focusing from aninfinitely distant object to a close distance object.

In the variable magnification optical system according to the SecondExample, the B group G4B is moved, as a vibration reduction group, tohave a component in a direction perpendicular to the optical axis,thereby conducting vibration reduction. Meanwhile, upon carrying outvibration reduction, positions of the A group G4A and the C group G4C ina direction perpendicular to the optical axis are fixed.

It is noted that in the variable magnification optical system accordingto the Second Example, in the wide angle end state, the vibrationreduction coefficient is 1.17, and the focal length is 71.35 (mm), sothat the moving amount of the B group G4B for correcting a rotationalcamera shake of 0.30 degrees is 0.32 (mm). In the telephoto end state,the vibration reduction coefficient is 1.80, and the focal length is294.00 (mm), so that the moving amount of the B group G4B for correctinga rotational camera shake of 0.20 degrees is 0.57 (mm).

Table 2 below shows various values of the variable magnification opticalsystem according to the Second Example.

TABLE 2 Second Example [Surface Data] Surface number r d nd νd ObjectPlane ∞  1 84.0136 6.369 1.51680 63.88  2 −569.5201 0.287  3 111.79621.500 1.62004 36.40  4 36.8295 8.708 1.51680 63.88  5 239.6437 variable 6 −196.3998 1.000 1.69680 55.52  7 17.8250 4.472 1.80518 25.45  863.8758 2.220  9 −50.1550 1.000 1.80100 34.92 10 107.3132 variable 1198.4276 3.799 1.51680 63.88 12 −44.7987 variable 13 33.5689 5.2211.48749 70.31 14 −34.6171 1.000 1.75520 27.57 15 −464.1612 1.880 16(Stop S) ∞ 31.253  17 −215.7008 3.558 1.80610 40.97 18 −18.9067 1.0001.69680 55.52 19 29.6933 2.000 20 25.4517 4.902 1.51742 52.20 21−34.1288 6.212 22 −19.1689 1.000 1.77250 49.62 23 −46.3649 BF ImagePlane ∞ [Various Data] Variable magnification ratio 4.12 W M T f 71.4105.0 294.0 FNO 4.70 4.74 6.44 2ω 22.84 15.30 5.46 Ymax 14.25 14.2514.25 TL 167.32 188.67 222.32 BF 38.52 39.12 64.52 Infinitely distant d53.000 27.419 53.254 d10 29.124 23.882 2.000 d12 9.294 10.871 15.165Close distance d5 3.000 27.419 53.254 d10 29.965 25.078 3.487 d12 8.4539.675 13.679 [Lens Group Data] Group Starting Surface f 1 1 128.484 2 6−29.436 3 11 60.115 4 13 180.542 [Values for Conditional Expression] (1)fA/(−fB) = 2.468 (1A) f1/(−fc) = 4.365 (1B) f1fw/ff = 3.954 (2) f1/ff =2.137 (3) ff/fi = 0.333 (4) fi/(−fB) = 3.886 (5) νFP = 63.88 (6) ff/ft =0.204

FIGS. 6A, 6B and 6C are graphs showing various aberrations of thevariable magnification optical system according to the Second Exampleupon focusing on an infinitely distant object, in which FIG. 6A is in awide angle end state, FIG. 6B is in an intermediate focal length state,and FIG. 6C is in a telephoto end state.

FIG. 7A is a graph showing meridional transverse aberration of thevariable magnification optical system according to the Second Exampleupon focusing on an infinitely distant object in the wide angle endstate with carrying out vibration reduction against a rotational camerashake of 0.30 degrees, and FIG. 7B is a graph showing meridionaltransverse aberration of the variable magnification optical systemaccording to the Second Example upon focusing on an infinitely distantobject in the telephoto end state with carrying out vibration reductionagainst a rotational camera shake of 0.20 degrees.

FIGS. 8A, 8B and 8C are graphs showing various aberrations of thevariable magnification optical system according to the Second Exampleupon focusing on a close distance object, in which FIG. 8A is in thewide angle end state, FIG. 8B is in the intermediate focal length state,and FIG. 8C is in the telephoto end state.

As is apparent from the respective aberration graphs, the variablemagnification optical system according to the Second Example showssuperb imaging performance as a result of good corrections to variousaberrations in the wide angle end state to the telephoto end state, andalso shows superb imaging performance upon carrying out vibrationreduction and upon focusing on a close distance object.

THIRD EXAMPLE

FIG. 9 is a sectional view of a variable magnification optical systemaccording to a Third Example.

The variable magnification optical system according to the Third Exampleis composed of, in order from an object side, a first lens group G1having positive refractive power, a second lens group G2 having negativerefractive power, and a rear group GR having positive refractive power.The rear group GR is composed of, in order from the object side, a thirdlens group G3 having positive refractive power, and a fourth lens groupG4 having positive refractive power.

The first lens group G1 consists of, in order from the object side, adouble convex positive lens L11, and a cemented positive lensconstructed by a negative meniscus lens L12 having a convex surfacefacing the object side cemented with a positive meniscus lens L13 havinga convex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented negative lens constructed by a double concave negative lens L21cemented with a positive meniscus lens L22 having a convex surfacefacing the object side, and a double concave negative lens L23.

The third lens group G3 consists of a double convex positive lens L31.

The fourth lens group G4 is composed of, in order from the object side,an A group G4A having positive refractive power, a B group G4B havingnegative refractive power, and a C group G4C having positive refractivepower. Meanwhile, an aperture stop S is disposed between the A group G4Aand the B group G4B.

The A group G4A consists of, in order from the object side, a cementedpositive lens constructed by a double convex positive lens L41 cementedwith a negative meniscus lens L42 having a concave surface facing theobject side.

The B group G4B consists of, in order from the object side, a cementednegative lens constructed by a positive meniscus lens L43 having aconcave surface facing the object side cemented with a double concavenegative lens L44.

The C group G4C consists of, in order from the object side, a doubleconvex positive lens L45, and a cemented negative lens constructed by adouble concave negative lens L46 cemented with a double convex positivelens L47.

In the variable magnification optical system according to the ThirdExample, the first to fourth lens groups G1 to G4 are moved along theoptical axis so that, upon varying magnification between the wide angleend state and the telephoto end state, a distance between the first lensgroup G1 and the second lens group G2, a distance between the secondlens group G2 and the third lens group G3 and a distance between thethird lens group G3 and the fourth lens group G4 are varied.

In the variable magnification optical system according to the ThirdExample, the third lens group G3 is moved toward an image side along theoptical axis, as the focusing lens group, thereby focusing from aninfinitely distant object to a close distance object.

In the variable magnification optical system according to the ThirdExample, the B group G4B is moved, as a vibration reduction group, tohave a component in a direction perpendicular to the optical axis,thereby conducting vibration reduction. Meanwhile, upon carrying outvibration reduction, positions of the A group G4A and the C group G4C ina direction perpendicular to the optical axis are fixed.

It is noted that in the variable magnification optical system accordingto the Third Example, in the wide angle end state, the vibrationreduction coefficient is 1.22, and the focal length is 71.40 (mm), sothat the moving amount of the B group G4B for correcting a rotationalcamera shake of 0.30 degrees is 0.31 (mm). In the telephoto end state,the vibration reduction coefficient is 1.79, and the focal length is294.00 (mm), so that the moving amount of the B group G4B for correctinga rotational camera shake of 0.20 degrees is 0.57 (mm).

Table 3 below shows various values of the variable magnification opticalsystem according to the Third Example.

TABLE 3 Third Example [Surface Data] Surface number r d nd νd ObjectPlane ∞  1 85.0462 5.776 1.51680 63.88  2 −660.6172 0.468  3 127.38021.500 1.62004 36.40  4 39.1726 7.903 1.51680 63.88  5 338.5447 variable 6 −132.1891 1.000 1.69680 55.52  7 19.2602 4.667 1.80518 25.45  876.0183 2.071  9 −54.4201 1.000 1.80100 34.92 10 119.2030 variable 11101.6158 3.707 1.51680 63.88 12 −48.1136 variable 13 32.8274 5.3391.48749 70.31 14 −36.1413 1.000 1.80518 25.45 15 −208.8127 1.719 16(Stop S) ∞ 20.897  17 −111.8106 3.901 1.66755 41.87 18 −18.5066 1.0001.58913 61.22 19 35.2076 2.000 20 26.2172 5.000 1.48749 70.31 21−44.8232 10.387  22 −18.5590 1.000 1.77250 49.62 23 39.9065 4.0061.60342 38.03 24 −29.6411 BF Image Plane ∞ [Various Data] Variablemagnification ratio 4.12 W M T f 71.4 105.0 294.0 FNO 4.68 4.76 6.45 2ω22.80 15.28 5.44 Ymax 14.25 14.25 14.25 TL 166.39 188.89 221.32 BF 38.5239.12 64.52 Infinitely distant d5 3.000 27.909 54.414 d10 30.861 25.2462.000 d12 9.676 12.274 16.047 Close distance d5 3.000 27.909 54.414 d1031.772 26.533 3.581 d12 8.765 10.987 14.466 [Lens Group Data] GroupStarting Surface f 1 1 130.814 2 6 −30.984 3 11 63.720 4 13 184.004[Values for Conditional Expression] (1) fA/(−fB) = 1.836 (1A) f1/(−fc) =4.222 (1B) f1fw/ff = 3.924 (2) f1/ff = 2.063 (3) ff/fi = 0.345 (4)fi/(−fB) = 3.433 (5) νFP = 63.88 (6) ff/ft = 0.216

FIGS. 10A, 10B and 10C are graphs showing various aberrations of thevariable magnification optical system according to the Third Exampleupon focusing on an infinitely distant object, in which FIG. 10A is in awide angle end state, FIG. 10B is in an intermediate focal length state,and FIG. 10C is in a telephoto end state.

FIG. 11A is a graph showing meridional transverse aberration of thevariable magnification optical system according to the Third Exampleupon focusing on an infinitely distant object in the wide angle endstate with carrying out vibration reduction against a rotational camerashake of 0.30 degrees, and FIG. 11B is a graph showing meridionaltransverse aberration of the variable magnification optical systemaccording to the Third Example upon focusing on an infinitely distantobject in the telephoto end state with carrying out vibration reductionagainst a rotational camera shake of 0.20 degrees.

FIGS. 12A, 12B and 12C are graphs showing various aberrations of thevariable magnification optical system according to the Third Exampleupon focusing on a close distance object, in which FIG. 12A is in thewide angle end state, FIG. 12B is in the intermediate focal lengthstate, and FIG. 12C is in the telephoto end state.

As is apparent from the respective aberration graphs, the variablemagnification optical system according to the Third Example shows superbimaging performance as a result of good corrections to variousaberrations in the wide angle end state to the telephoto end state, andalso shows superb imaging performance upon carrying out vibrationreduction and upon focusing on a close distance object.

FOURTH EXAMPLE

FIG. 13 is a sectional view of a variable magnification optical systemaccording to a Fourth Example.

The variable magnification optical system according to the FourthExample is composed of, in order from an object side, a first lens groupG1 having positive refractive power, a second lens group G2 havingnegative refractive power, and a rear group GR having positiverefractive power. The rear group GR is composed of, in order from theobject side, a third lens group G3 having positive refractive power anda fourth lens group G4 having positive refractive power.

The first lens group G1 consists of, in order from the object side, adouble convex positive lens L11, and a cemented positive lensconstructed by a negative meniscus lens L12 having a convex surfacefacing the object side cemented with a positive meniscus lens L13 havinga convex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented negative lens constructed by a double concave negative lens L21cemented with a positive meniscus lens L22 having a convex surfacefacing the object side, and a double concave negative lens L23.

The third lens group G3 consists of a double convex positive lens L31.

The fourth lens group G4 is composed of, in order from the object side,an A group G4A having positive refractive power, a B group G4B havingnegative refractive power, and a C group G4C having positive refractivepower. Meanwhile, an aperture stop S is disposed between the A group G4Aand the B group G4B.

The A group G4A consists of, in order from the object side, a cementedpositive lens constructed by a double convex positive lens L41 cementedwith a negative meniscus lens L42 having a concave surface facing theobject side.

The B group G4B consists of, in order from the object side, a cementednegative lens constructed by a positive meniscus lens L43 having aconcave surface facing the object side cemented with a double concavenegative lens L44.

The C group G4C consists of, in order from the object side, a doubleconvex positive lens L45, and a cemented negative lens constructed by adouble concave negative lens L46 cemented with a double convex positivelens L47.

In the variable magnification optical system according to the FourthExample, the first to fourth lens groups G1 to G4 are moved along theoptical axis so that, upon varying magnification between the wide angleend state and the telephoto end state, a distance between the first lensgroup G1 and the second lens group G2, a distance between the secondlens group G2 and the third lens group G3 and a distance between thethird lens group G3 and the fourth lens group G4 are varied.

In the variable magnification optical system according to the FourthExample, the third lens group G3 is moved toward an image side along theoptical axis, as the focusing lens group, thereby focusing from aninfinitely distant object to a close distance object.

In the variable magnification optical system according to the FourthExample, the B group G4B is moved, as a vibration reduction group, tohave a component in a direction perpendicular to the optical axis,thereby conducting vibration reduction. Meanwhile, upon carrying outvibration reduction, positions of the A group G4A and the C group G4C ina direction perpendicular to the optical axis are fixed.

It is noted that in the variable magnification optical system accordingto the Fourth Example, in the wide angle end state, the vibrationreduction coefficient is 1.21, and the focal length is 71.40 (mm), sothat the moving amount of the B group G4B for correcting a rotationalcamera shake of 0.30 degrees is 0.31 (mm). In the telephoto end state,the vibration reduction coefficient is 1.79, and the focal length is292.00 (mm), so that the moving amount of the B group G4B for correctinga rotational camera shake of 0.20 degrees is 0.57 (mm).

Table 4 below shows various values of the variable magnification opticalsystem according to the Fourth Example.

TABLE 4 Fourth Example [Surface Data] Surface number r d nd νd ObjectPlane ∞  1 86.4475 5.443 1.51680 63.88  2 −981.1690 0.200  3 146.33781.500 1.62004 36.40  4 41.2453 8.000 1.51680 63.88  5 1154.1773 variable 6 −105.1301 1.000 1.69680 55.52  7 20.4832 4.124 1.80518 25.45  877.3629 1.964  9 −62.6354 1.000 1.83400 37.18 10 142.2611 variable 11123.7504 3.431 1.58913 61.22 12 −57.1062 variable 13 33.8130 5.6341.49700 81.73 14 −38.7693 1.000 1.80518 25.45 15 −194.5892 1.688 16(Stop S) ∞ 21.000  17 −99.8095 3.775 1.66755 41.87 18 −18.8632 1.0001.58913 61.22 19 36.8056 2.500 20 34.3226 3.724 1.51680 63.88 21−51.2601 11.445  22 −20.6818 1.000 1.77250 49.62 23 51.2093 3.8541.60342 38.03 24 −30.0976 BF Image Plane ∞ [Various Data] Variablemagnification ratio 4.09 W M T f 71.4 100.0 292.0 FNO 4.70 4.69 6.48 2ω22.78 16.04 5.48 Ymax 14.25 14.25 14.25 TL 169.32 189.52 221.32 BF 39.1238.52 66.12 Infinitely distant d5 3.000 26.086 53.441 d10 32.425 27.5612.000 d12 11.493 14.070 16.477 Close distance d5 3.000 26.086 53.441 d1033.360 28.885 3.621 d12 10.558 12.746 14.856 [Lens Group Data] GroupStarting Surface f 1 1 128.221 2 6 −31.614 3 11 66.796 4 13 176.525[Values for Conditional Expression] (1) fA/(−fB) = 1.691 (1A) f1/(−fc) =4.056 (1B) f1fw/ff = 4.017 (2) f1/ff = 1.920 (3) ff/fi = 0.378 (4)fi/(−fB) = 3.308 (5) νFP = 61.22 (6) ff/ft = 0.229

FIGS. 14A, 14B and 14C are graphs showing various aberrations of thevariable magnification optical system according to the Fourth Exampleupon focusing on an infinitely distant object, in which FIG. 14A is in awide angle end state, FIG. 14B is in an intermediate focal length state,and FIG. 14C is in a telephoto end state.

FIG. 15A is a graph showing meridional transverse aberration of thevariable magnification optical system according to the Fourth Exampleupon focusing on an infinitely distant object in the wide angle endstate with carrying out vibration reduction against a rotational camerashake of 0.30 degrees, and FIG. 15B is a graph showing meridionaltransverse aberration of the variable magnification optical systemaccording to the Fourth Example upon focusing on an infinitely distantobject in the telephoto end state with carrying out vibration reductionagainst a rotational camera shake of 0.20 degrees.

FIGS. 16A, 16B and 16C are graphs showing various aberrations of thevariable magnification optical system according to the Fourth Exampleupon focusing on a close distance object, in which FIG. 16A is in thewide angle end state, FIG. 16B is in the intermediate focal lengthstate, and FIG. 16C is in the telephoto end state.

As is apparent from the respective aberration graphs, the variablemagnification optical system according to the Fourth Example showssuperb imaging performance as a result of good corrections to variousaberrations in the wide angle end state to the telephoto end state, andalso shows superb imaging performance upon carrying out vibrationreduction and upon focusing on a close distance object.

FIFTH EXAMPLE

FIG. 17 is a sectional view of a variable magnification optical systemaccording to a Fifth Example.

The variable magnification optical system according to the Fifth Exampleis composed of, in order from an object side, a first lens group G1having positive refractive power, a second lens group G2 having negativerefractive power, and a rear group GR having positive refractive power.The rear group GR is composed of, in order from the object side, a thirdlens group G3 having positive refractive power, and a fourth lens groupG4 having positive refractive power.

The first lens group G1 consists of, in order from the object side, adouble convex positive lens L11, and a cemented positive lensconstructed by a negative meniscus lens L12 having a convex surfacefacing the object side cemented with a positive meniscus lens L13 havinga convex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented negative lens constructed by a double concave negative lens L21cemented with a positive meniscus lens L22 having a convex surfacefacing the object side, and a double concave negative lens L23.

The third lens group G3 consists of a double convex positive lens L31.

The fourth lens group G4 is composed of, in order from the object side,an A group G4A having positive refractive power, a B group G4B havingnegative refractive power, and a C group G4C having positive refractivepower. Meanwhile, an aperture stop S is disposed between the A group G4Aand the B group G4B.

The A group G4A consists of, in order from the object side, a cementedpositive lens constructed by a double convex positive lens L41 cementedwith a negative meniscus lens L42 having a concave surface facing theobject side.

The B group G4B consists of, in order from the object side, a cementednegative lens constructed by a positive meniscus lens L43 having aconcave surface facing the object side cemented with a double concavenegative lens L44.

The C group G4C consists of, in order from the object side, a cementedpositive lens constructed by a double convex positive lens L45 cementedwith a negative meniscus lens L46 having a concave surface facing theobject side, and a negative meniscus lens L47 having a concave surfacefacing the object side.

In the variable magnification optical system according to the FifthExample, the first to fourth lens groups G1 to G4 are moved along theoptical axis so that, upon varying magnification between the wide angleend state and the telephoto end state, a distance between the first lensgroup G1 and the second lens group G2, a distance between the secondlens group G2 and the third lens group G3 and a distance between thethird lens group G3 and the fourth lens group G4 are varied.

In the variable magnification optical system according to the FifthExample, the third lens group G3 is moved toward an image side along theoptical axis, as the focusing lens group, thereby focusing from aninfinitely distant object to a close distance object.

In the variable magnification optical system according to the FifthExample, the B group G4B is moved, as a vibration reduction group, tohave a component in a direction perpendicular to the optical axis,thereby conducting vibration reduction. Meanwhile, upon carrying outvibration reduction, positions of the A group G4A and the C group G4C ina direction perpendicular to the optical axis are fixed.

It is noted that in the variable magnification optical system accordingto the Fifth Example, in the wide angle end state, the vibrationreduction coefficient is 1.61, and the focal length is 72.10 (mm), sothat the moving amount of the B group G4B for correcting a rotationalcamera shake of 0.30 degrees is 0.23 (mm). In the telephoto end state,the vibration reduction coefficient is 2.44, and the focal length is292.00 (mm), so that the moving amount of the B group G4B for correctinga rotational camera shake of 0.20 degrees is 0.42 (mm).

Table 5 below shows various values of the variable magnification opticalsystem according to the Fifth Example.

TABLE 5 Fifth Example [Surface Data] Surface number r d nd νd ObjectPlane ∞  1 90.0000 5.600 1.51680 63.88  2 −517.3850 0.200  3 123.08151.700 1.62004 36.40  4 39.0000 7.800 1.51680 63.88  5 324.1762 variable 6 −110.0000 1.300 1.69680 55.52  7 21.2201 3.957 1.84666 23.80  873.0429 1.848  9 −75.3714 1.200 1.85026 32.35 10 106.1768 variable 11148.9696 3.374 1.58913 61.22 12 −56.4978 variable 13 28.2564 5.7461.49700 81.73 14 −48.4258 1.200 1.84666 23.80 15 −580.3411 2.897 16(Stop S) ∞ 23.051  17 −77.0000 3.951 1.72825 28.38 18 −14.4874 1.0001.67003 47.14 19 29.3362 2.500 20 29.8903 5.510 1.62004 36.40 21−17.4201 1.000 1.84666 23.80 22 −35.2773 7.314 23 −22.7541 1.000 1.7725049.62 24 −46.2730 BF Image Plane ∞ [Various Data] variable magnificationratio 4.05 W M T f 72.1 100.0 292.0 FNO 4.70 4.63 6.53 2ω 22.62 16.085.50 Ymax 14.25 14.25 14.25 TL 169.32 187.97 221.32 BF 39.61 38.52 66.61Infinitely distant d5 3.001 26.619 53.461 d10 33.373 28.524 2.000 d1211.187 12.162 17.100 Close distance d5 3.001 26.619 53.461 d10 34.37229.969 3.698 d12 10.188 10.718 15.402 [Lens Group Data] Group StartingSurface f 1 1 131.155 2 6 −32.550 3 11 69.956 4 13 165.331 [Values forConditional Expression] (1) fA/(−fB) = 2.356 (1A) f1/(−fc) = 4.029 (1B)f1fw/ff = 4.519 (2) f1/ff = 1.902 (3) ff/fi = 0.417 (4) fi/(−fB) = 4.755(5) νFP = 61.22 (6) ff/ft = 0.236

FIGS. 18A, 18B and 18C are graphs showing various aberrations of thevariable magnification optical system according to the Fifth Exampleupon focusing on an infinitely distant object, in which FIG. 18A is in awide angle end state, FIG. 18B is in an intermediate focal length state,and FIG. 18C is in a telephoto end state.

FIG. 19A is a graph showing meridional transverse aberration of thevariable magnification optical system according to the Fifth Exampleupon focusing on an infinitely distant object in the wide angle endstate with carrying out vibration reduction against a rotational camerashake of 0.30 degrees, and FIG. 19B is a graph showing meridionaltransverse aberration of the variable magnification optical systemaccording to the Fifth Example upon focusing on an infinitely distantobject in the telephoto end state with carrying out vibration reductionagainst a rotational camera shake of 0.20 degrees.

FIGS. 20A, 20B and 20C are graphs showing various aberrations of thevariable magnification optical system according to the Fifth Exampleupon focusing on a close distance object, in which FIG. 20A is in thewide angle end state, FIG. 20B is in the intermediate focal lengthstate, and FIG. 20C is in the telephoto end state.

As is apparent from the respective aberration graphs, the variablemagnification optical system according to the Fifth Example shows superbimaging performance as a result of good corrections to variousaberrations in the wide angle end state to the telephoto end state, andalso shows superb imaging performance upon carrying out vibrationreduction and upon focusing on a close distance object.

SIXTH EXAMPLE

FIG. 21 is a sectional view of a variable magnification optical systemaccording to a Sixth Example.

The variable magnification optical system according to the Sixth Exampleis composed of, in order from an object side, a first lens group G1having positive refractive power, a second lens group G2 having negativerefractive power, and a rear group GR having positive refractive power.The rear group GR is composed of, in order from the object side, a thirdlens group G3 having positive refractive power, and a fourth lens groupG4 having positive refractive power.

The first lens group G1 consists of, in order from the object side, adouble convex positive lens L11, and a cemented positive lensconstructed by a negative meniscus lens L12 having a convex surfacefacing the object side cemented with a positive meniscus lens L13 havinga convex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented negative lens constructed by a double concave negative lens L21cemented with a positive meniscus lens L22 having a convex surfacefacing the object side, and a double concave negative lens L23.

The third lens group G3 consists of a double convex positive lens L31.

The fourth lens group G4 is composed of, in order from the object side,an A group G4A having positive refractive power, a B group G4B havingnegative refractive power, and a C group G4C having positive refractivepower. Meanwhile, an aperture stop S is disposed between the A group G4Aand the B group G4B.

The A group G4A consists of, in order from the object side, a cementedpositive lens constructed by a double convex positive lens L41 cementedwith a double concave negative lens L42, and a double convex positivelens L43.

The B group G4B consists of, in order from the object side, a cementednegative lens constructed by a negative meniscus lens L44 having aconcave surface facing the object side cemented with a double concavenegative lens L45.

The C group G4C consists of, in order from the object side, a doubleconvex positive lens L46, and a negative meniscus lens L47 having aconcave surface facing the object side.

In the variable magnification optical system according to the SixthExample, the first to fourth lens groups G1 to G4 are moved along theoptical axis so that, upon varying magnification between the wide angleend state and the telephoto end state, a distance between the first lensgroup G1 and the second lens group G2, a distance between the secondlens group G2 and the third lens group G3 and a distance between thethird lens group G3 and the fourth lens group G4 are varied.

In the variable magnification optical system according to the SixthExample, the third lens group G3 is moved toward an image side along theoptical axis, as the focusing lens group, thereby focusing from aninfinitely distant object to a close distance object.

In the variable magnification optical system according to the SixthExample, the B group G4B is moved, as a vibration reduction group, tohave a component in a direction perpendicular to the optical axis,thereby conducting vibration reduction. Meanwhile, upon carrying outvibration reduction, positions of the A group G4A and the C group G4C ina direction perpendicular to the optical axis are fixed.

It is noted that in the variable magnification optical system accordingto the Sixth Example, in the wide angle end state, the vibrationreduction coefficient is 1.54, and the focal length is 72.10 (mm), sothat the moving amount of the B group G4B for correcting a rotationalcamera shake of 0.30 degrees is 0.25 (mm). In the telephoto end state,the vibration reduction coefficient is 2.42, and the focal length is292.00 (mm), so that the moving amount of the B group G4B for correctinga rotational camera shake of 0.20 degrees is 0.42 (mm).

Table 6 below shows various values of the variable magnification opticalsystem according to the Sixth Example.

TABLE 6 Sixth Example [Surface Data] Surface number r d nd νd ObjectPlane ∞  1 94.0000 5.600 1.51680 63.88  2 −475.5757 0.200  3 128.00001.700 1.62004 36.40  4 39.6000 8.000 1.51680 63.88  5 425.5305 variable 6 −190.0000 1.300 1.69680 55.52  7 20.4656 4.300 1.84666 23.80  866.5049 2.063  9 −61.8359 1.200 1.85026 32.35 10 109.1965 variable 11128.7113 3.300 1.58913 61.22 12 −63.7222 variable 13 37.0000 5.4001.49700 81.73 14 −45.9212 1.300 1.85026 32.35 15 148.3744 0.200 1645.1050 3.600 1.48749 70.31 17 −172.8812 4.000 18 (Stop S) ∞ 26.764  19−95.3704 3.900 1.74950 35.25 20 −14.2257 1.000 1.69680 55.52 21 24.15702.279 22 26.2427 4.000 1.62004 36.40 23 −55.0000 2.250 24 −20.2886 1.0001.84666 23.80 25 −34.0000 BF Image Plane ∞ [Various Data] Variablemagnification ratio 4.05 W M T f 72.1 100.0 292.0 FNO 4.69 4.66 6.54 2ω22.56 16.04 5.50 Ymax 14.25 14.25 14.25 TL 169.32 189.24 221.32 BF 38.9338.52 65.93 Infinitely distant d5 2.500 25.118 52.806 d10 33.481 28.5572.155 d12 11.047 13.692 17.068 Close distance d5 2.500 25.118 52.806 d1034.454 29.917 3.849 d12 10.075 12.332 15.373 [Lens Group Data] GroupStarting Surface f 1 1 130.472 2 6 −32.352 3 11 72.809 4 13 142.608[Values for Conditional Expression] (1) fA/(−fB) = 2.479 (1A) f1/(−fc) =4.033 (1B) f1fw/ff = 6.295 (2) f1/ff = 1.792 (3) ff/fi = 0.511 (4)fi/(−fB) = 4.779 (5) νFP = 61.22 (6) ff/ft = 0.249

FIGS. 22A, 22B and 22C are graphs showing various aberrations of thevariable magnification optical system according to the Sixth Exampleupon focusing on an infinitely distant object, in which FIG. 22A is in awide angle end state, FIG. 22B is in an intermediate focal length state,and FIG. 22C is in a telephoto end state.

FIG. 23A is a graph showing meridional transverse aberration of thevariable magnification optical system according to the Sixth Exampleupon focusing on an infinitely distant object in the wide angle endstate with carrying out vibration reduction against a rotational camerashake of 0.30 degrees, and FIG. 23B is a graph showing meridionaltransverse aberration of the variable magnification optical systemaccording to the Sixth Example upon focusing on an infinitely distantobject in the telephoto end state with carrying out vibration reductionagainst a rotational camera shake of 0.20 degrees.

FIGS. 24A, 24B and 24C are graphs showing various aberrations of thevariable magnification optical system according to the Sixth Exampleupon focusing on a close distance object, in which FIG. 24A is in thewide angle end state, FIG. 24B is in the intermediate focal lengthstate, and FIG. 24C is in the telephoto end state.

As is apparent from the respective aberration graphs, the variablemagnification optical system according to the Sixth Example shows superbimaging performance as a result of good corrections to variousaberrations in the wide angle end state to the telephoto end state, andalso shows superb imaging performance upon carrying out vibrationreduction and upon focusing on a close distance object.

SEVENTH EXAMPLE

FIG. 25 is a sectional view of a variable magnification optical systemaccording to a Seventh Example.

The variable magnification optical system according to the SeventhExample is composed of, in order from an object side, a first lens groupG1 having positive refractive power, a second lens group G2 havingnegative refractive power, and a rear group GR having positiverefractive power. The rear group GR is composed of, in order from theobject side, a third lens group G3 having positive refractive power, anda fourth lens group G4 having positive refractive power.

The first lens group G1 consists of, in order from the object side, adouble convex positive lens L11, and a cemented positive lensconstructed by a negative meniscus lens L12 having a convex surfacefacing the object side cemented with a positive meniscus lens L13 havinga convex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented negative lens constructed by a double concave negative lens L21cemented with a positive meniscus lens L22 having a convex surfacefacing the object side, and a double concave negative lens L23.

The third lens group G3 consists of a double convex positive lens L31.

The fourth lens group G4 is composed of, in order from the object side,an A group G4A having positive refractive power, a B group G4B havingnegative refractive power, and a C group G4C having positive refractivepower. Meanwhile, an aperture stop S is disposed between the A group G4Aand the B group G4B.

The A group G4A consists of, in order from the object side, a cementedpositive lens constructed by a double convex positive lens L41 cementedwith a double concave negative lens L42, and a double convex positivelens L43.

The B group G4B consists of, in order from the object side, a cementednegative lens constructed by a positive meniscus lens L44 having aconcave surface facing the object side cemented with a double concavenegative lens L45.

The C group G4C consists of, in order from the object side, a doubleconvex positive lens L46, and a negative meniscus lens L47 having aconcave surface facing the object side.

In the variable magnification optical system according to the SeventhExample, the first to fourth lens groups G1 to G4 are moved along theoptical axis so that, upon varying magnification between the wide angleend state and the telephoto end state, a distance between the first lensgroup G1 and the second lens group G2, a distance between the secondlens group G2 and the third lens group G3 and a distance between thethird lens group G3 and the fourth lens group G4 are varied.

In the variable magnification optical system according to the SeventhExample, the third lens group G3 is moved toward an image side along theoptical axis, as the focusing lens group, thereby focusing from aninfinitely distant object to a close distance object.

In the variable magnification optical system according to the SeventhExample, the B group G4B is moved, as a vibration reduction group, tohave a component in a direction perpendicular to the optical axis,thereby conducting vibration reduction. Meanwhile, upon carrying outvibration reduction, positions of the A group G4A and the C group G4C ina direction perpendicular to the optical axis are fixed.

It is noted that in the variable magnification optical system accordingto the Seventh Example, in the wide angle end state, the vibrationreduction coefficient is 1.61, and the focal length is 72.10 (mm), sothat the moving amount of the B group G4B for correcting a rotationalcamera shake of 0.30 degrees is 0.23 (mm). In the telephoto end state,the vibration reduction coefficient is 2.42, and the focal length is292.00 (mm), so that the moving amount of the B group G4B for correctinga rotational camera shake of 0.20 degrees is 0.42 (mm).

Table 7 below shows various values of the variable magnification opticalsystem according to the Seventh Example.

TABLE 7 Seventh Example [Surface Data] Surface number r d nd νd ObjectPlane ∞  1 94.0000 5.600 1.51680 63.88  2 −477.1369 0.200  3 127.99541.700 1.62004 36.40  4 39.7182 8.000 1.51680 63.88  5 477.0326 variable 6 −133.8008 1.300 1.69680 55.52  7 20.5210 4.000 1.84666 23.80  868.1000 2.028  9 −63.5000 1.200 1.85026 32.35 10 113.2367 variable 11102.3130 3.400 1.58913 61.22 12 −69.1650 13 39.2000 5.500 1.49700 81.7314 −39.2000 1.300 1.85026 32.35 15 209.5771 0.200 16 50.7811 3.7001.48749 70.31 17 −101.5494 1.393 18 (Stop S) ∞ 22.905  19 −80.0000 3.3001.80100 34.92 20 −18.0344 1.000 1.70000 48.11 21 29.8801 2.000 2234.2607 3.800 1.60342 38.03 23 −54.3498 7.014 24 −20.2978 1.000 1.7725049.62 25 −34.3298 BF Image plane ∞ [Various Data] Variable magnificationratio 4.05 W M T f 72.1 100.0 292.0 FNO 4.71 4.68 6.51 2ω 22.58 16.045.50 Ymax 14.25 14.25 14.25 TL 169.32 188.35 221.32 BF 42.82 42.30 69.82Infinitely distant d5 2.500 25.131 52.658 d10 32.209 27.505 2.151 d1211.251 12.875 16.152 Close distance d5 2.500 25.131 52.658 d10 33.11628.781 3.756 d12 10.345 11.599 14.546 [Lens Group Data] Group StartingSurface f 1 1 128.381 2 6 −31.506 3 11 70.567 4 13 143.423 [Values forConditional Expression] (1) fA/(−fB) = 2.044 (1A) f1/(−fc) = 4.075 (1B)f1fw/ff = 6.330 (2) f1/ff = 1.819 (3) ff/fi = 0.492 (4) fi/(−fB) = 4.048(5) νFP = 61.22 (6) ff/ft = 0.242

FIGS. 26A, 26B and 26C are graphs showing various aberrations of thevariable magnification optical system according to the Seventh Exampleupon focusing on an infinitely distant object, in which FIG. 26A is in awide angle end state, FIG. 26B is in an intermediate focal length state,and FIG. 26C is in a telephoto end state.

FIG. 27A is a graph showing meridional transverse aberration of thevariable magnification optical system according to the Seventh Exampleupon focusing on an infinitely distant object in the wide angle endstate with carrying out vibration reduction against a rotational camerashake of 0.30 degrees, and FIG. 27B is a graph showing meridionaltransverse aberration of the variable magnification optical systemaccording to the Seventh Example upon focusing on an infinitely distantobject in the telephoto end state with carrying out vibration reductionagainst a rotational camera shake of 0.20 degrees.

FIGS. 28A, 28B and 28C are graphs showing various aberrations of thevariable magnification optical system according to the Seventh Exampleupon focusing on a close distance object, in which FIG. 28A is in thewide angle end state, FIG. 28B is in the intermediate focal lengthstate, and FIG. 28C is in the telephoto end state.

As is apparent from the respective aberration graphs, the variablemagnification optical system according to the Seventh Example showssuperb imaging performance as a result of good corrections to variousaberrations in the wide angle end state to the telephoto end state, andalso shows superb imaging performance upon carrying out vibrationreduction and upon focusing on a close distance object.

EIGHTH EXAMPLE

FIG. 29 is a sectional view of a variable magnification optical systemaccording to an Eighth Example.

The variable magnification optical system according to the EighthExample is composed of, in order from an object side, a first lens groupG1 having positive refractive power, a second lens group G2 havingnegative refractive power, and a rear group GR having positiverefractive power. The rear group GR is composed of, in order from theobject side, a third lens group G3 having positive refractive power, afourth lens group G4 having positive refractive power, and a fifth lensgroup G5 having negative refractive power.

The first lens group G1 consists of, in order from the object side, adouble convex positive lens L11, and a cemented positive lensconstructed by a negative meniscus lens L12 having a convex surfacefacing the object side cemented with a positive meniscus lens L13 havinga convex surface facing the object side.

The second lens group G2 consists of, in order from the object side, acemented negative lens constructed by a double concave negative lens L21cemented with a positive meniscus lens L22 having a convex surfacefacing the object side, and a double concave negative lens L23.

The third lens group G3 consists of a double convex positive lens L31.

The fourth lens group G4 is composed of, in order from the object side,an A group G4A having positive refractive power, a B group G4B havingnegative refractive power, and a C group G4C having positive refractivepower. Meanwhile, an aperture stop S is disposed between the A group G4Aand the B group G4B.

The A group G4A consists of, in order from the object side, a cementedpositive lens constructed by a double convex positive lens L41 cementedwith a double concave negative lens L42, and a double convex positivelens L43.

The B group G4B consists of, in order from the object side, a cementednegative lens constructed by a positive meniscus lens L44 having aconcave surface facing the object side cemented with a double concavenegative lens L45.

The C group G4C consists of a double convex positive lens L46.

The fifth lens group G5 consists of a negative meniscus lens L51 havinga concave surface facing the object side.

In the variable magnification optical system according to the EighthExample, the first to the fifth lens groups G1 to G5 are moved along theoptical axis so that, upon varying magnification between the wide angleend state and the telephoto end state, a distance between the first lensgroup G1 and the second lens group G2, a distance between the secondlens group G2 and the third lens group G3, a distance between the thirdlens group G3 and the fourth lens group G4 and a distance between thefourth lens group G4 and the fifth lens group G5 are varied.

In the variable magnification optical system according to the EighthExample, the third lens group G3 is moved toward an image side along theoptical axis, as the focusing lens group, thereby focusing from aninfinitely distant object to a close distance object.

In the variable magnification optical system according to the EighthExample, the B group G4B is moved, as a vibration reduction group, tohave a component in a direction perpendicular to the optical axis,thereby conducting vibration reduction. Meanwhile, upon carrying outvibration reduction, positions of the A group G4A and the C group G4C ina direction perpendicular to the optical axis are fixed.

It is noted that in the variable magnification optical system accordingto the Eighth Example, in the wide angle end state, the vibrationreduction coefficient is 1.62, and the focal length is 72.10 (mm), sothat the moving amount of the B group G4B for correcting a rotationalcamera shake of 0.30 degrees is 0.23 (mm). In the telephoto end state,the vibration reduction coefficient is 2.42, and the focal length is292.00 (mm), so that the moving amount of the B group G4B for correctinga rotational camera shake of 0.20 degrees is 0.42 (mm).

Table 8 below shows various values of the variable magnification opticalsystem according to the Eighth Example.

TABLE 8 Eighth Example [Surface Data] Surface number r d nd νd ObjectPlane ∞  1 94.0000 5.600 1.51680 63.88  2 −475.1178 0.200  3 128.00001.700 1.62004 36.40  4 39.6000 8.000 1.51680 63.88  5 485.7465 variable 6 −132.5210 1.300 1.69680 55.52  7 20.5172 4.000 1.84666 23.80  868.1000 2.042  9 −63.5000 1.200 1.85026 32.35 10 115.6235 variable 11101.8918 3.400 1.58913 61.22 12 −69.9544 variable 13 39.2000 5.5001.49700 81.73 14 −39.2000 1.300 1.85026 32.35 15 212.6596 0.200 1651.4164 3.700 1.48749 70.31 17 −99.0728 1.373 18 (Stop S) ∞ 23.152  19−80.0000 3.300 1.80100 34.92 20 −17.8244 1.000 1.70000 48.11 21 29.43022.000 22 34.1234 3.800 1.60342 38.03 23 −54.6969 variable 24 −20.34661.000 1.77250 49.62 25 −34.1069 BF Image Plane ∞ [Various Data] Variablemagnification ratio 4.05 W M T f 72.1 100.0 292.0 FNO 4.71 4.69 6.49 2ω22.58 16.06 5.50 Ymax 14.25 14.25 14.25 TL 169.32 188.16 221.32 BF 43.0742.89 70.02 Infinitely distant d5 2.500 24.944 52.518 d10 32.517 27.8452.150 d12 10.875 12.288 16.347 d23 6.586 6.430 6.515 Close distance d52.500 24.944 52.518 d10 33.434 29.131 3.779 d12 9.958 11.001 14.718 d236.586 6.430 6.515 [Lens Group Data] Group Starting Surface f 1 1 128.1382 6 −31.607 3 11 70.925 4 13 71.734 5 24 −67.420 [Values for ConditionalExpression] (1) fA/(−fB) = 2.058 (1A) f1/(−fc) = 4.054 (1B) f1fw/ff =6.215 (2) f1/ff = 1.807 (3) ff/fi = 0.989 (4) fi/(−fB) = 2.046 (5) νFP =61.22 (6) ff/ft = 0.243

FIGS. 30A, 30B and 30C are graphs showing various aberrations of thevariable magnification optical system according to the Eighth Exampleupon focusing on an infinitely distant object, in which FIG. 30A is in awide angle end state, FIG. 30B is in an intermediate focal length state,and FIG. 30C is in a telephoto end state.

FIG. 31A is a graph showing meridional transverse aberration of thevariable magnification optical system according to the Eighth Exampleupon focusing on an infinitely distant object in the wide angle endstate with carrying out vibration reduction against a rotational camerashake of 0.30 degrees, and FIG. 31B is a graph showing meridionaltransverse aberration of the variable magnification optical systemaccording to the Eighth Example upon focusing on an infinitely distantobject in the telephoto end state with carrying out vibration reductionagainst a rotational camera shake of 0.20 degrees.

FIGS. 32A, 32B and 32C are graphs showing various aberrations of thevariable magnification optical system according to the Eighth Exampleupon focusing on a close distance object, in which FIG. 32A is in thewide angle end state, FIG. 32B is in the intermediate focal lengthstate, and FIG. 32C is in the telephoto end state.

As is apparent from the respective aberration graphs, the variablemagnification optical system according to the Eighth Example showssuperb imaging performance as a result of good corrections to variousaberrations in the wide angle end state to the telephoto end state, andalso shows superb imaging performance upon carrying out vibrationreduction and upon focusing on a close distance object.

According to the above-mentioned examples, it is possible to realize avariable magnification optical system which can superbly suppressvariations in various aberrations upon varying magnification from thewide angle end state to the telephoto end state and variations invarious aberrations upon focusing from an infinitely distant object to aclose distance object and can downsize a focusing group and make itlight in weight. That is, in this variable magnification optical system,by downsizing the focusing group and making it light in weight, thefocusing group can be driven by a small-sized motor or mechanicalmechanism, thereby realizing a high speed and silent focusing operationwith avoiding enlargement of a lens barrel.

Note that each of the above described Examples is a concrete example ofthe invention of the present application, and the invention of thepresent application is not limited to them. The contents described belowcan be properly adopted without deteriorating optical performance of thevariable magnification optical systems according to the embodiment ofthe present application.

Although the variable magnification optical systems each having a fouror five group configuration are illustrated above as examples of thevariable magnification optical systems according to the embodiment ofthe present application, the present application is not limited to themand the variable magnification optical systems having otherconfigurations, such as a six group configuration and the like, can beconfigured. Concretely, a configuration that a lens or a lens group isadded to a most object side or a most image side of the variablemagnification optical system according to each of the above-mentionedexamples is also possible.

Further, in each of the above-mentioned examples, the second lens groupis illustrated as an intermediate group disposed at an image side of thefirst lens group and having negative refractive power, but the presentinvention is not limited to such configuration. Further, in each of theabove-mentioned examples, the third lens group is illustrated as afocusing group disposed at an image side of the second lens group as anintermediate group and having positive refractive power, but the presentinvention is not limited to such configuration. Further, in each of theabove-mentioned examples, the fourth lens group is illustrated as animage side group disposed at an image side of the focusing group andhaving positive refractive power, but the present invention is notlimited to such configuration. Concretely, it is also possible that alens group having a positive or negative refractive power is disposedbetween the first lens group and the intermediate group (the second lensgroup) and distances between these lens groups are varied upon varyingmagnification. Further, it is also possible that a lens group having apositive or negative refractive power is disposed between theintermediate group (the second lens group) and the focusing group (thethird lens group) and distances between these lens groups are variedupon varying magnification. Further, it is also possible that a lensgroup having a positive or negative refractive power is disposed betweenthe focusing group (the third lens group) and the image side group (thefourth lens group) and distances between these lens groups are variedupon varying magnification.

In the variable magnification optical system according to each of theabove-mentioned examples, it is preferable that the vibration reductiongroup is disposed at an image side of the focusing group, and it is morepreferable that other lens(es) is(are) disposed between the focusinggroup and the vibration reduction group. Further, regarding the reargroup, in a case where other lens(es) is(are) disposed between thefocusing group and the vibration reduction group, it is preferable thatan air distance between a lens facing an object side of the vibrationreduction group and the vibration reduction group is the largest one ofthe air distances in the rear group.

Further, regarding the rear group, it is preferable that an aperturestop is disposed between the focusing group and the vibration reductiongroup, and it is more preferable that an aperture stop is disposed at aposition facing an object side of the vibration reduction group.Meanwhile, the function of an aperture stop may be substituted by a lensframe without disposing a member as the aperture stop.

Further, the refractive power of the C group is positive in each of theExamples, but it may be negative.

Further, a sub-combination of feature groups of respective examples alsois deemed as an invention of the present application.

Further, in the variable magnification optical system according to eachof the above-mentioned examples, the whole third lens group is used as afocusing group, but a part of lens group or two or more lens groups maybe used as a focusing group. Further, it is preferable that the focusinggroup has a positive refractive power. Further, one or two lenscomponents are enough for configuration of the focusing group, but morepreferably the focusing group is composed of one lens component. Thefocusing group can be used for auto focus, and also can be suitablydriven by a motor for auto focus, for example, an ultrasonic motor, astepping motor, a VCM motor or the like.

Further, in the variable magnification optical system according to eachof the above-mentioned examples, any lens group in the entirety thereofor a portion thereof can be shifted in a direction including a componentperpendicular to the optical axis as a vibration reduction group, orrotationally moved (swayed) in an in-plane direction including theoptical axis for conducting vibration reduction. Particularly, in thevariable magnification optical system according to each of theabove-mentioned examples, it is preferable that the B group is used as avibration reduction group. Further, although vibration reduction groupmay be composed of one cemented lens as in each of the above-mentionedexamples, it may be also composed of a single lens or two or more lenscomponents without particularly limiting the number of lenses. Further,it is preferable that the vibration reduction group has negativerefraction power. Further, it is preferable that the vibration reductiongroup is composed of a part of one lens group, and it is more preferablethat one lens group is divided into three parts and the vibrationreduction group is composed of a center part of the three parts.Furthermore, it is preferable that one lens group is divided into threepositive-negative-positive parts or positive-negative-negative parts,and the vibration reduction group is composed of a center negative partof the three parts.

Further, in the variable magnification optical system according to eachof the above-mentioned examples, a lens surface of a lens may be aspherical surface, a plane surface, or an aspherical surface. Further,each lens may be formed by a glass material, a resin material or acomposite of a glass material and a resin material. When a lens surfaceis a spherical surface or a plane surface, lens processing and assemblyadjustment become easy, so that deterioration in optical performancecaused by a lens processing error and an assembly adjustment error canbe prevented and thus it is preferable. Moreover, even if the imageplane is shifted, deterioration in optical performance is littleconveniently. When a lens surface is an aspherical surface, theaspherical surface may be fabricated by a grinding process, a glassmolding process that a glass material is formed into an aspherical shapeby a mold, or a compound type process that a resin material on a glasssurface is formed into an aspherical shape. Further, a lens surface maybe a diffractive optical surface, and a lens may be a graded-index typelens (GRIN lens) or a plastic lens.

Moreover, lens surfaces of lenses configuring the variable magnificationoptical system according to each example may be coated withanti-reflection coating. With this contrivance, it is feasible to reducea flare as well as ghost and attain high contrast and high opticalperformance. Particularly, in the variable magnification optical systemaccording to each of the above-mentioned examples, it is preferable tocoat an object side lens surface of the second lens counted from a mostobject side with anti-reflection coating.

Next, a camera equipped with a variable magnification optical systemaccording to an embodiment of the present application, will be explainedwith referring to FIG. 33.

FIG. 33 is a sectional view showing a configuration of the cameraequipped with the variable magnification optical system according to theembodiment of the present application.

As shown in FIG. 33, a camera 1 is a so-called mirrorless camera oflens-replaceable type equipped with the variable magnification opticalsystem according to the above-mentioned First Example as an imaging lens2.

In the present camera 1, light emitted from an unillustrated object isconverged by the imaging lens 2, and an object image is formed on animaging surface of an imaging unit 3 through an unillustrated OLPF(Optical low pass filter). Then, the object image is photo-electricallyconverted by a photoelectric conversion element in the imaging unit 3 togenerate an image of the object. This image is displayed on an EVF(Electronic view finder) 4 mounted in the camera 1. Accordingly, aphotographer can observe the object image through the EVF 4.

Further, when the photographer presses an unillustrated release buttondown, the image of the object generated in the imaging unit 3 is storedin an unillustrated memory. In this manner, the photographer can take apicture of an object by the present camera 1.

Hence, the variable magnification optical system according to the aboveFirst Example, mounted as the imaging lens 2 in the present camera 1,has excellent optical performance and a focusing lens group reduced inweight. That is, the present camera 1 can realize excellent opticalperformance and high speed focusing operation. Moreover, even when acamera is configured to mount thereon the variable magnification opticalsystem according to each of the above Second to Eighth Examples, as theimaging lens 2, the camera can provide the same advantageous effects asthe above camera 1 can do. Further, even when the variable magnificationoptical system according to each of the above examples is mounted on acamera of single-lens reflex type having a quick return mirror andobserving an object by a finder optical system, the camera can providethe same advantageous effects as the above camera 1 can do.

Finally, an outline of a method for manufacturing a variablemagnification optical system according to the present embodiment, isdescribed with referring to FIG. 34.

FIG. 34 is a flowchart showing an outline of a method for manufacturingthe variable magnification optical system according to the presentembodiment.

A method for manufacturing a variable magnification optical systemaccording to the present embodiment as shown in FIG. 34 comprises a stepS1 of preparing a first lens group disposed at a most object side andhaving positive refractive power, an intermediate group disposed at animage side of the first lens group and having negative refractive power,a focusing group disposed at an image side of the intermediate group andhaving positive refractive power, the focusing group being moved uponfocusing, and an image side group disposed at an image side of thefocusing group and having positive refractive power, and a step S2 ofarranging the first lens group, the intermediate group, the focusinggroup, and the image side group such that, upon varying magnification, adistance between the first lens group and the intermediate group, adistance between the intermediate group and the focusing group and adistance between the focusing group and the image side group are varied,the image side group being composed of, in order from an object side, anA group having positive refractive power, a B group satisfying thefollowing conditional expression (1) with respect to the A group andhaving negative refractive power, and a C group:

1.67<fA/(−fB)<2.80   (1)

where fA denotes a focal length of the A group, and fB denotes a focallength of the B group.

According to the method for manufacturing a variable magnificationoptical system of the present embodiment, it is possible to manufacturea variable magnification optical system having excellent opticalperformance and a focusing lens group reduced in weight in order toattain high speed focusing operation.

What is claimed is:
 1. A variable magnification optical system,comprising: a first lens group disposed at a most object side and havingpositive refractive power; an intermediate group disposed at an imageside of the first lens group and having negative refractive power; afocusing group disposed at an image side of the intermediate group andhaving positive refractive power, the focusing group being moved uponfocusing; and an image side group disposed at an image side of thefocusing group and having positive refractive power; upon varyingmagnification, a distance between the first lens group and theintermediate group, a distance between the intermediate group and thefocusing group and a distance between the focusing group and the imageside group being varied; the image side group comprising, in order froman object side, an A group having positive refractive power, a B groupsatisfying the following conditional expression with respect to the Agroup and having negative refractive power, and a C group:1.67<fA/(−fB)<2.80 where fA denotes a focal length of the A group, andfB denotes a focal length of the B group; and the following conditionalexpression being satisfied:2.50<f1/(−fc)≤4.365 where f1 denotes a focal length of the first lensgroup, and fc denotes a focal length of the intermediate group.
 2. Avariable magnification optical system according to claim 1, wherein thefollowing conditional expression is satisfied:0.25<ff/fi<1.10 where ff denotes a focal length of the focusing group,and fi denotes a focal length of the image side group.
 3. A variablemagnification optical system according to claim 1, wherein the followingconditional expression is satisfied:1.80<fi/(−fB)<5.20 where fi denotes a focal length of the image sidegroup.
 4. A variable magnification optical system according to claim 1,wherein the focusing group comprises at least one positive lens and thefollowing conditional expression is satisfied:58.00<νFP where νFP denotes an Abbe number for d-line (wavelength 587.6nm) of the positive lens.
 5. A variable magnification optical system,comprising: a first lens group disposed at a most object side and havingpositive refractive power; an intermediate group disposed at an imageside of the first lens group and having negative refractive power; afocusing group disposed at an image side of the intermediate group andhaving positive refractive power, the focusing group being moved uponfocusing; and an image side group disposed at an image side of thefocusing group and having positive refractive power; upon varyingmagnification, a distance between the first lens group and theintermediate group, a distance between the intermediate group and thefocusing group and a distance between the focusing group and the imageside group being varied; the image side group comprising, in order froman object side, an A group having positive refractive power, a B groupsatisfying the following conditional expression with respect to the Agroup and having negative refractive power, and a C group:1.67<fA/(−fB)<2.80 where fA denotes a focal length of the A group, andfB denotes a focal length of the B group; and the following conditionalexpression being satisfied:0.492≤ff/fi<1.10 where ff denotes a focal length of the focusing group,and fi denotes a focal length of the image side group.
 6. A variablemagnification optical system according to claim 5, wherein the followingconditional expression is satisfied:2.50<f1/(−fc)<6.20 where f1 denotes a focal length of the first lensgroup, and fc denotes a focal length of the intermediate group.
 7. Avariable magnification optical system according to claim 5, wherein thefollowing conditional expression is satisfied:1.80<fi/(−fB)<5.20.
 8. A variable magnification optical system accordingto claim 5, wherein the focusing group comprises at least one positivelens and the following conditional expression is satisfied:58.00<νFP where νFP denotes an Abbe number for d-line (wavelength 587.6nm) of the positive lens.
 9. A variable magnification optical system,comprising: a first lens group disposed at a most object side and havingpositive refractive power; an intermediate group disposed at an imageside of the first lens group and having negative refractive power; afocusing group disposed at an image side of the intermediate group andhaving positive refractive power, the focusing group being moved uponfocusing; and an image side group disposed at an image side of thefocusing group and having positive refractive power; upon varyingmagnification, a distance between the first lens group and theintermediate group, a distance between the intermediate group and thefocusing group and a distance between the focusing group and the imageside group being varied; and the image side group comprising, in orderfrom an object side, an A group having positive refractive power, a Bgroup satisfying the following conditional expression with respect tothe A group and having negative refractive power, and a C group:1.67<fA/(−fB)≤1.836 where fA denotes a focal length of the A group, andfB denotes a focal length of the B group.
 10. A variable magnificationoptical system according to claim 9, wherein the following conditionalexpression is satisfied:2.50<f1/(−fc)<6.20 where f1 denotes a focal length of the first lensgroup, and fc denotes a focal length of the intermediate group.
 11. Avariable magnification optical system according to claim 9, wherein thefollowing conditional expression is satisfied:0.25<ff/fi<1.10 where ff denotes a focal length of the focusing group,and fi denotes a focal length of the image side group.
 12. A variablemagnification optical system according to claim 9, wherein the followingconditional expression is satisfied:1.80<fi/(−fB)<5.20 where fi denotes a focal length of the image sidegroup.
 13. A variable magnification optical system according to claim 9,wherein the focusing group comprises at least one positive lens and thefollowing conditional expression is satisfied:58.00<νFP where νFP denotes an Abbe number for d-line (wavelength 587.6nm) of the positive lens.
 14. A method for manufacturing a variablemagnification optical system, comprising steps of: arranging a firstlens group disposed at a most object side and having positive refractivepower, an intermediate group disposed at an image side of the first lensgroup and having negative refractive power, a focusing group disposed atan image side of the intermediate group and having positive refractivepower, the focusing group being moved upon focusing, and an image sidegroup disposed at an image side of the focusing group and havingpositive refractive power; the arrangement being such that, upon varyingmagnification, a distance between the first lens group and theintermediate group, a distance between the intermediate group and thefocusing group and a distance between the focusing group and the imageside group are varied; and the method further comprising at least one ormore of the following features (A), (B) and (C): (A) configuring theimage side group to comprise, in order from an object side, an A grouphaving positive refractive power, a B group satisfying the followingconditional expression with respect to the A group and having negativerefractive power, and a C group:1.67<fA/(−fB)<2.80 where fA denotes a focal length of the A group, andfB denotes a focal length of the B group, and satisfying the followingconditional expression:2.50<f1/(−fc)≤4.365 where f1 denotes a focal length of the first lensgroup, and fc denotes a focal length of the intermediate group; (B)configuring the image side group to comprise, in order from an objectside, an A group having positive refractive power, a B group satisfyingthe following conditional expression with respect to the A group andhaving negative refractive power, and a C group:1.67<fA/(−fB)<2.80 where fA denotes a focal length of the A group, andfB denotes a focal length of the B group, and satisfying the followingconditional expression:0.492≤ff/fi<1.10 where ff denotes a focal length of the focusing group,and fi denotes a focal length of the image side group; (C) configuringthe image side group to comprise, in order from an object side, an Agroup having positive refractive power, a B group satisfying thefollowing conditional expression with respect to the A group and havingnegative refractive power, and a C group:1.67<fA/(−fB)≤1.836 where fA denotes a focal length of the A group, andfB denotes a focal length of the B group.